Vol. 10, Special Issue 6 (2025)

Author(s): Ibrahem A Abdulzahra and Samer Riyadh Fadhil

Abstract: The bronchial tree in mammals changes step by step as it branches from the trachea into the lungs. In cattle, these changes help the lungs regulate airflow, clear mucus, and exchange gases. This study compared the tissue structure of extra-pulmonary and intra-pulmonary bronchi in adult Bos taurus. Samples were collected after slaughter. The tissues were processed using standard histological methods. Sections were stained with hematoxylin-eosin (H&E) to show general structures and with periodic acid-Schiff (PAS) to highlight mucopolysaccharides. The slides were examined under 4x, 10x, and 40x magnifications. The extra-pulmonary bronchi showed clear features. The lining was pseudostratified columnar epithelium with tall ciliated cells and many goblet cells. Submucosal glands were plentiful. Cartilage plates were thick and continuous, providing strong support. Smooth muscle layers were well developed below the mucosa, helping control the airway before it enters the lung. Intra-pulmonary bronchi had thinner and irregular cartilage plates. The epithelium stayed pseudostratified but had more PAS-positive goblet cells and stronger gland secretions. The smooth muscle layer was thinner. The connective tissue became softer and more flexible to match the lung tissue. These results show clear tissue changes as the bronchi move into the lung. The differences reflect how the bronchi adapt to airflow control, mucus production, and the need for flexibility during breathing in cattle.